Traditionally, thermal printing is used to produce labels that can be applied to objects such as containers, books, computer disks, equipment or the like. Typical thermal image label printers are manufactured by Brother of Japan and Kroy, Inc. of Scottsdale, Ariz.
Generally, thermal image printers provide input capabilities, power and a housing designed to accept a label cartridge containing the material used to form the label. The label cartridge generally includes one or more spools of material that are combined and fed over a thermal printing head to generate an image on a label.
In conventional systems, the label is formed from three basic components: a plastic or wax ink coated on a plastic ribbon film, a paper or plastic ink receiving layer, and an adhesive backing layer.
In operation, the plastic ribbon with the ink and receiving layer are passed over the heating element of the thermal printing head, which melts the ink on the plastic ribbon so that it adheres to the receiving layer. The heating element is selectively heated, based on the input to the printing apparatus, to print letters, symbols or the like, on the receiving layer, while leaving ink on the plastic film that is not needed to form the image. After the plastic ribbon and receiving layer are passed over the heating element, the plastic ribbon is removed from the receiving layer to expose the image produced on the receiving layer. If the adhesive backing has not already been applied to the back of the receiving layer, opposite the side that received the ink, the adhesive layer is applied to the receiving layer and the final label is outputted from the cartridge and the printer. Once outputted, the label may be applied to an object for identification.
Labels produced by this method of printing have several drawbacks. First, since the ink is melted onto the receiving layer, the image tends to blur around the edges, with the amount of blurring being dependent on the type of ink and the type of receiving layer. Second, the image produced on the receiving layer is exposed and can be affected by light, weather or rubbing so that the image on the label is ultimately unusable and must be replaced.
To overcome these drawbacks, better inks and receiving layers have been produced to provide sharper images. However, these procedures increase costs. In addition, laminating a clear layer over the image on the receiving layer to cover and protect the image has been done. However, this step requires extra material and extra steps to produce the laminated product, which increases the cost of the label. Also, application of the clear layer may further blur the image, with the amount of blurring being dependent on the manner in which the clear layer is applied to the receiving layer.
Ink jet printers have also be used to generate labels. However, labels generated by inkjet printers suffer from many of the same drawbacks that thermal image labels suffered from. For example, the image is exposed and can be affected by light weather and rubbing so that the image on the label is ultimately unusable and must be replaced. Also, many ink jet inks are water based and subject to smearing and deterioration when exposed to moisture.